The invention relates generally to data recovery of storage technologies, and more particularly to systems, methods, apparatuses and systems for data recovery by adaptive and selective cancellation of inter-symbol interference of a read channel of storage technologies.
Advances in manufacturing technologies and system architecture have led to increasingly powerful consumer electronic devices and computers. These consumer electronic devices and computers support features and applications, such as multimedia, in connection with which vast amounts of information are processed and stored. Generally, the amount of information is not only vast, but also ever-increasing.
To provide the information, storage technologies have been developed, including magnetic, optical and magneto-optical technologies. Although these technologies provide relatively large storage capabilities, the technologies generally demand ongoing improvement so as to overcome factors limiting storage capacity. Among other areas for ongoing improvement is the accurate detection of recorded data, particularly while increasing the recording density.
Detection of recorded data is conventionally accomplished using a threshold. As an example, channel bits of an optical read channel (using, for example, 1,7 run-length-limited modulation coding) are detected by comparing a read signal to a predetermined threshold: if the read signal exceeds the threshold at a particular channel-bit location, that channel-bit is considered a `1` (i.e., a mark); otherwise the channel-bit is considered a `0` (i.e., a space).
Detection against a threshold relies on setting an appropriate threshold. Generally, the threshold is set toward recovering recorded information within an acceptable bit error rate. To do so, the threshold optimally is set to the center of an "eye-pattern", the eye-pattern being a measure that indicates the amplitude and phase margins of the read signal. However, the read signal's amplitude and phase margins tend to be affected by various parameters, including, among others, the write power, the write sensitivity of the media, the quality of the spot of the write and read drives (e.g., mark size variations), and the focus offset of the write and read drives. Because these parameters vary across systems and media, the center of the eye pattern tends to vary and, in turn, the optimal threshold setting tends to vary.
Moreover, increasing recording density tends to increase inter-symbol interference ("ISI"). Recording density is associated with, e.g., reduction in channel-bit length and/or, for optical disk media, variation in radial position. Inter-symbol interference, in turn, tends to raise the level of the read signal of spaces between adjacent marks. If such raised level approaches or exceeds the threshold, the bit error rate generally increases.
Accordingly, it is desirable to provide for accurate detection of recorded data while accommodating increased recording density.